Analysis of genotypic diversity based on leaf morphological traits in rockets (Eruca sativa)

Leaf morphological traits such as, leaf number, leaf margin index and leaf hairiness were measured to assess the genetic diversity of baby leaf rocket.. In this research, leaf number was

Analysis of genotypic diversity based on leaf

morphological traits in rockets (Eruca sativa)

Zhi‐Hao Xu1, Ngoc‐Thang Vu2,3, Si‐Hong Kim2 and Il‐Seop Kim2

1 Vegetables Institute, Zhejiang Academy of Agricultural Science, Hangzhou, China; 2 Department of Horticulture, Kangwon National University, Chuncheon, Korea; 3 Faculty of Agronomy, Vietnam National University of Agriculture, Hanoi, Vietnam

Abstract

This research was carried out to evaluate the genetic diversity of salad rocket based on leaf morphological traits Total 213 of rocket genotypes were used in this experiment and they were grouped as native and non-native genotypes, further each group were subdivided as cultivated and wild Leaf morphological traits such as, leaf number, leaf margin index and leaf hairiness were measured to assess the genetic diversity of baby leaf rocket In this research, leaf number was found higher and leaf distribution pattern was wider range in native cultivated rocket among the genotypes

No distinguish differences of leaf hairiness was found among the genotype but 20 genotypes from native cultivated rocket has shown some degree of hairiness Large genotype variation in leaf margin index was found among the genotypes The results stated that rocket leaves characteristics could be used as an important parameter in

breeding of Eruca sativa for further improvement of its quality

Keywords: breeding, genetic diversity, leaf morphology, leaf number, leaf number

distribution

INTRODUCTION

The rocket plant (Eruca sativa Mill.) is an important leafy vegetable belonging to the

family Brassicaceae that have a pungent aroma and a sharp taste Rocket is used in many ways, as condiment in salads, cooked vegetables, medicinal and functional plants (Kim et al., 2006) Besides its popular uses as vegetables, rocket is also considered a medicinal plant The leaves of rocket salad have been used for thousands of year to season food, oil for the production of deodorants and cosmetics and for medicinal purposes (Pratap and Gupta, 2009) Increased interest in these species was largely a result of the International Plant Genetic Resources Institute (IPGRI) workshops, which were held in 1994 in Lisbon, Portugal (Padulosi and Pignone, 1997) The assessment of agronomical and morphological traits of salad rockets is an effective tool for making progress in crop improvement (Bello et al., 2006)

Despite the increasing of economic importance of rocket plant limited information is available on genetic variability of leaf phenotypic traits of various genotypes of rockets Hence, leaf morphological study association with plant properties are necessities for a successful further rocket breeding The objective of this study was to examine the leaf phenotypic variability of 213 genotypes of rocket including native and non‐native species for their further breeding

MATERIALS AND METHODS

Plant materials and growing conditions

A total of 213 genotypes of salad rocket were grown in the experimental field The evaluated genotypes were collected from different countries viz Afghanistan, China, Egypt, India, Iran, Italy, Pakistan, and Turkey They were grouped as native wild, native cultivated, non‐native wild and non‐native cultivated according to the historical records of germplasm accessions (Table 1) The seeds of rockets were first sown in the nursing trays filled with commercial growing substrate and kept in glasshouse When the seedlings had 2‐3 true

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leaves, 20 seedlings for each genotype were transplanted in a hydroponic system The glasshouse climate was auto‐controlled with a Priva greenhouse climate computer The temperature in the greenhouse was set 28/15°C for day and night, respectively No carbon dioxide enrichment was used during this experiment The nutrient solution was made by using commercial fertilizer (Wonder Grow, Chobi Co., Ltd, Korea), consisting percentage of N:P:K:Mg:Br:S:Mn:Fe:Zn such as 10:8:25:2:0.1:5:0.05:0.05:0.01, respectively The nutrient solution was adjusted to pH 5.8‐6.8 and 1.7‐2.0 mS cm‐1 for EC twice a week The nutrient solution was recycled five times a day The nutrient solution was renewed in two weeks interval to ensure the balance and sufficiency of nutrient

Table 1 Total number of rocket genotypes used in this experiment

Data collection

The leaf morphological traits of rocket were observed two weeks after transplanting The morphological traits obtained were: leaf margin index, leaf hairiness and leaf number The experiment was arranged in completely randomized design in four replications

RESULTS

The genotype variation of leaf number in rockets

The leaf number data from all the 213 genotypes of rocket were found as showed in Figure 1 The average value of leaf number was higher in cultivated genotypes of rocket than wild genotypes Among the genotypes higher leaf number was found in native cultivated genotype (Figure 1) Most of genotypes had 5‐8 leaves per plant, with a distribution peak at 6‐7 leaves for genotypes from native and non‐native area (Figure 2) More native genotypes were distributed in the range of higher leaf number than the non‐native genotypes, and similarly, more cultivated genotypes had higher range of leaf number than the wild genotypes (Figure 3) The cultivated genotypes had wider distribution range in leaf number from 3 to 11

Figure 1 The comparison of leaf number in rocket genotypes from native or non‐native

area and wild or cultivated rockets

Figure 2 The distribution of leaf number in rocket genotypes from native and non‐native

area

Figure 3 The distribution of leaf number in wild and cultivated rocket genotypes

The genotype variation of leaf margin index in rocket

The leaf margin index was calculated from individual plant for each genotype When the individual plant had a tooth type of leaf margin, it got a score of 1 While the plant had smooth type of leaf margin, it got a score of 0 The data in Figure 4 showed that there was a large genotype variation in the type of leaf margin Among the 213 genotypes, 95 genotypes had uniform tooth type of leaf margin and two genotypes showed smooth leaf margin In other 116 genotypes, individuals with tooth type or smooth type of leaf margin were found

in the same genotypes, which suggested the poor uniformity in these genotypes

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Figure 4 The leaf margin in rocket genotypes grouped as native wild (NW), native

cultivated (NC), non‐native wild (CW) and non‐native cultivated (CC)

The genotype variation of leaf hairiness in rocket genotypes

In case of leaf hairiness, most genotypes of rocket had not shown the distinguish hairiness on the leaf Only 20 genotypes mainly in the group of cultivated genotypes from native area showed some degree of hairiness, and 4 of them shad very hairy leaves and stems (Figure 5)

Figure 5 The leaf hairiness in rocket genotypes grouped as native wild (NW), native

cultivated (NC), non‐native wild (CW) and non‐native cultivated (CC)

DISCUSSION

Recent years the rocket production as baby leaf vegetable for ready‐to‐eat salad is getting more popular in many countries The selection of new cultivars suitable for growing

in soilless culture systems is of great interest It is important to evaluate the genotypic variation for the cultivar selection and new cultivar breeding The leaf number was higher in the genotypes from native area than those from non‐native area It was the same for cultivated genotypes in comparison of wild genotypes (Figure 1) Native cultivated genotypes showed higher leaf number and were distributed in the higher range comparing

to the wild genotypes and genotypes from non‐native area Leaf is the main edible part of rocket, so the knowledge on leaf physiological variations among the genotypes is very important for cultivation and breeding Morphological variations are established on the origin of specific genotypes either native or non‐native Morphological differences are based

on genetic variation spread throughout the entire genome (Bratteler et al., 2006) A high

degree of agronomical and morphological traits variations were also found in Silene vulgaris genotypes (Egea‐Gilabert et al., 2013) which resemble to our finding for Eruca sativa

These data could lead to a suggestion, despite of the complicate source history and variation among the genotypes, the cultivated genotypes and the genotypes of non‐native area had received more human efforts which resulted from the farmer breeders, who tend to select the faster growth and later bolting of plants for a better crop production The heavy hairy leaf is rare in the rocket genotypes, as this characteristics cause the rough feeling when rocket is consumed These genotypes are possibly rejected during the seeds saving by the farmers

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Egea‐Gilabert, C., Niñirola, N., Conesa, E., Candela, M.E., and Fernández, J.A (2013) Agronomical use as baby leaf

salad of Silene vulgaris based on morphological, biochemical and molecular traits Sci Hortic (Amsterdam) 152,

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